Dual string circulating valve

ABSTRACT

The dual string circulating valve utilizes a dual-mandrel hydraulically actuated valving system to be used as a circulating valve in a well utilizing dual production strings and is adapted to be inserted in the string below tools like the dual string packer. The valve operates by pressuring one string to open a port through that mandrel to the casing annulus, with closing and locking of the port being accomplished by pressurizing the other string.

0 v United States Patent 11 1 1111 3,871,450 Jett et al. Mar. 18, 1975 [54] DUAL STRING CIRCULATING VALVE 3,467,185 9/1969 Dowden l66/147 3,572,434 3 197l Ecue 1 Inventors: Seagovlllei 3,750,752 8l1973 MOIt 166/224 R sprlggs, Dallas both of 3,799,268 3/1974 Cochran l66/3l3 A ig Dresser Industries, Inc. Dallas, Tex MOII [22] Filed: 1974 Primary E.\'aminerJames A. Leppink 2 APPL 461,684 Attorney, Agent, or Firm-Michael J. Caddell 52 us. 01 166/224 R, 137/595, 166/147, [57] ABST RACT 1 /151 251/ 2 The dual strmg circulating valve ut1lizes a dual- [51 Int. Cl E21b 41/00, E2lb 43/14 mandrel hydraulically actuated valving System to [53] Fi ld f s h 16 /115 147 224 R 224 A, used as a circulating valve in a well utilizing dual pro- 1 313 151 134 154 39; 251 2 3; duction strings and is adapted to be inserted in the 137/594 595 string below tools like the dual string packer. The valve operates by pressuring one string to open a port [56] References Cited through that mandrel to the casing annulus, with clos- UNITED STATES PATENTS ing and locking of the port being accomplished by pressurizing the other string. 3,115,187 l2/l963 Brown 166/313 3,448,803 6/l969 Sizer 166/1 15 20 Claims, 7 Drawing Figures PATEHTEDHAR 1 81975 3.871.450 SHEET 2 BACKGROUND OF THE INVENTION In the completion and production of multi-zone oil wells and particularly dual-zone wells, a normal procedure for completion is to set a permanent packer in the casing between the producing formations and then lower a dual production string into the well so that one string will stab into the present permanent packer. The dual string will have a dual string packer contained therein which will be located in the string above the top producing formation. Examples of this dual string production packer are disclosed in US. Pat. applications Ser. No. 412,221; 412,239; and 412,386; all assigned to the assignee of this invention, and all herein incorporated by reference.

In many wells, particularly those which have been killed or which contain heavy displacement fluids, it is advantageous that, prior to the beginning of production, these fluids be circulated or pumped out of the two production strings. This is often accomplished by providing circulating valves in the dual string below the production packer, which valves may be opened to communicate the annulus with the inner bore of the strings so that a fluid pressure can be applied to the annulus fluid at the surface to displace it downward in the annulus and upward out of the production strings.

This requires the displacement to be achieved prior to setting the production packer in order that the annulus will remain open between-the surface and the circulating valves. Furthermore, this also requires physical manipulation of the strings to open and close the circulating valves. This manipulation also requires that the production packer remain unset during the operation of the circulating valves so that the tubing can be moved up and down.

This is undesirable in many circumstances because of the danger involved in a possible blowout while the production packer is unset, the heavy displacement mud is being removed, and the tubing is being moved upward or downward. All of these conditions are undesirable and may tend to increase the danger of a possible well blowout.

Another type of circulating tool available is dependent upon the operation of the packer and is only activated by setting of the production packer.

This invention provides a dual string, hydraulically operated circulating valve to be used with a dual string production packer, which circulating valve is actuated independently of the packer operation and without requiring manipulation of the tubing string.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view of a dual zone production formation having a dual production string;

FIG. 2 is a cross-sectional side view of the dual string circulating valve going in the hole;

FIG. 3 is an end cross-sectional view of the tool taken at line 33 of FIG. 2;

FIG. 4 is a cross-sectional side view of the tool after it has been actuated in the first or open stage;

FIG. 5 is an end cross-sectional view of the tool of FIG. 4 taken at line 5-5;

FIG. 6 is a cross-sectional side view of the dual circulating valve in its closed orientation;

FIG. 7 is an end cross-sectional view taken at line 7-7 of FIG. 6.

DESCRIPTION OF THE PREFERRED I EMBODIMENTS prior to the insertion of the dual string 2 in the well.

The long string 2a was stabbed" into the permanent packer 6 upon placing the dual string 2 in the well.

Packer 6 is located between the producing formations to isolate them from each other.

A dual production packer 7 was placed in the string before inserting in the well, and was located in the string so that it would be positioned above the upper producing formation 4. The dual packer 7 has a long string 2a extending through the permanent packer 6 and a short string 2b extending into the annulus be tween the permanent packer 6 and the dual packer 7.

The circulating valve 10 is located in the production string in the borehole below the dual packer 7. There are two bore passages 8 and 9 extending through the production string and continued through the dual circulating valve.

Referring to FIGS. 2 and 3, the valve 10 has an elongated tubular primary mandrel 11 and an elongated tubular secondary mandrel 12 arranged substantially in parallel orientation and coaxially aligned with the conduit of the dual production string. The two mandrels have upper adapter collars 13 and 14threadedly attached thereto for connection into the production string.

Valve collars 15 and 16 are threadedly attached to the lower ends of mandrels 11 and 12 respectively. Each valve collar has a valve seating sleeve 17 frangibly held concentrically therein by shear ring 18. Each sleeve 17 has a bevelled valve seat 19 at its upper end around an inner bore 20, said seat adapted to sealingly receive a valve member 21. O-ring seals 22 pass circumferentially around each sleeve 17 to provide a fluid tight seal betweensleeves l7 and collars l5 and 16. The lower end of each sleeve is threaded to receive another tubular section, with collar 15 having a lower or long string of conduit 23 threaded therein and collar 16 having a small stub-end 24 threaded therein. The tubular pieces threaded into the collars l5 and 16 serve to hold shear rings 18 clamped in abutment with valve sleeves 17. A small, shearable, outwardly extending peripheral lip 18a on the shear rings is held between a lower edge of the valve collars l5 and 16 and the upper end of tubular sections 23 and 24.

Mandrel 12 has one or more ports 25 through the wall thereof, and mandrel 11 has one or more ports 26 through the wall.

A primary piston body 27 is located slidably and relatively snugly about primary mandrel 11 and secondary mandrel 12 and covers ports 26. Mandrel 11 has an annular piston shoulder 28 extending outward into an inner enlarged annular chamber area 29 in body 27. Shoulder area 28 has an O-ring seal groove 30 with a seal 31 therein; a shear groove 32 and locking groove 33 below the seal groove 30.

An annular pressure responsive area 34 is located at the upper end of chamber 29 in body 27 and another annular pressure responsive area is formed on shoulder 28 of mandrel 11.

Body 27 has inner annular seal grooves 36 and 37 which contain circular seals 38 and 39 arranged to provide fluidic sealing between mandrel l1 and sleeve 27. Body 27 also has one or more large flow ports 40 passing through a lower extended skirt section 41 which skirt contains an enlarged inner bore 42.

A lower abutment ring 43 is securedly attached to mandrel 11 by means such as threads and abuts the lower end of shoulder 28 of the mandrel.

Secondary mandrel 12 has an upper exterior annular shoulder 44 formed thereon having a groove 45 therein in which is located resilient circular seal 46. A cylindrical, pressure-responsive closing sleeve 47 slidably encircles mandrel 12 and shoulder 44 in relatively snug fitting relationship. A radially inwardly projecting annular piston shoulder 48 is formed at the lower end of sleeve 47 and together with shoulder 44 forms expansion chamber 49. Shoulder 48 fits closely to mandrel 12 and contains in an annular groove 50 a resilient sealing ring 51 engaging the mandrel l2 and groove 50. Chamber 49 is arranged to communicate through the one or more ports 25 to bore 8.

Mandrel 12 passes in slightly loose-fitting relationship through a cylindrical bore 52 formed in body 27 so that mandrel 12 is loosely encircled by the body. This provides a substantial amount of lateral support against large distortions of mandrel. 12 away from mandrel 11 while also allowing the tool to be assembled in a most convenient manner. Limited upward and downward movement of mandrel 12 in body 27 is allowed although restrained past a certain point by the interaction of a two piece hard metal C-ring 53 in an annular external channel 54 formed in mandrel .12. C-ring .53 at its upper edge abuts an inner shoulder 55 of abutment ring 43 and at its lower edge abuts an assembly sleeve 56 which encircles mandrel 12 and is threadedly engaged in ring 43 into abutment with ring 53.

The interaction of shoulder 55 and sleeve 56 fixedly secures C-ring 53 to abutment ring 43. The channel 54 is of sufficient axial length to allow telescopic movement of mandrel 12 in and out of abutment ring 43 to allow assembly of the tool and attachment into the production string. This allows both vertical and rotational movement of the secondary mandrel within the body of an amount sufficient to allow ease in assembling the apparatus.

Mandrels 11 and 12 being secured together by ring 43 are further attached shearably to body 27 to prevent premature operation of the valve assembly such as when going in the hole. This is done by the placement of threaded shear screws 57 in body 27 which project radially inward toward primary mandrel 11 to engage in shear groove 32 in the mandrel. FIG. 3, which is an end cross-sectional view looking down the central axis of the piston body 27 from line 3-3 in FIG. 2, illustrates more clearly the shear screw assembly in the body 27 and mandrel 11.

In FIG. 3, a generally cylindrical shear screw 57 has a large threaded end 57a, a narrowed intermediate shear section 57b, and a groove engagement button 57c adapted to snugly engage in groove 32. Shear screw 57 has a slot or allen-head socket 57d for screwing the threaded section 57a into the threaded bore 58 in the body. 1

4 Also in FIG. 3 is shown a locking pin assembly 60 in a radial bore 59 in piston body 27. This assembly utilizes a generally cylindrical locking pin 61 slidably mounted in a relatively snug fit in bore 59 which is directed radially inward at mandrel 11. An external flange 61a at the outer end of pin 61 extends into abutment with an inwardly projecting annular shoulder 59a of bore 59 to limit movement of pin 61 inwardly.

A resilient element 62 such as a coil spring, belleville spring, or Z-spring is heldin compressive abutment against the outer end of pin 61 by a threaded plug 63 which is threadedly engaged in the threaded section of bore 59. Spring element 62 serves to keep pin 61 in contact with the mandrel until arecessed area on the mandrel comes under pin 61 such that shoulder 61a then abuts bore shoulder 59a. Pin 61 is necessarily larger than shear groove 32 to prevent its assuming a locking position in that groove. Locking groove 33 is sufficiently larger than pin 61 to allow it to seat therein and, because of abutment therewith, to lock piston body 27 and mandrel 11 together at the desired time.

In typical operation, the circulating valve assembly as illustrated in FIGS. 2 and 3 is attached to a dual production string below a dual production packer. A permanent packer is set in the borehole between the producing formations. The dual production string islowered into the borehole until the long string projecting downward from valve assembly 10 is stabbed into the permanent packer. The valve assembly 10 remains closed while going in the borehole.

After the long string is stabbed into the permanent packer and the production string is properly positioned in the well, the valve assembly may be actuated to circulate out the heavy drilling mud in the borehole. Actuation to the open position illustrated in FIGS. 4 and 5 is accomplished byapplying sufficient pressure to the primary string 11 to cause shearing of shear screws 57. Pressure may beapplied directly to the primary string if the lower formation is strong enough to withstand the pressure, or a valve element 21 may be dropped or pumped down the primary string to seat in valve seat sleeve 17. It should be noted that the absolute shear value of shear ring 18 should be substantially higher than the cumulative total shear value of all the shear screws 57 to insue proper operation of the valve assembly.

Upon application of pressure to the primary string, the pressure acts through ports 26 and chamber 29, against pressure responsive faces 34 and 35 thereby applying an upward force to piston sleeve 27 with respect to the mandrels. This force shears screws 57 thereby moving the piston sleeve 27 upward until ports 40 clear seal 31 and communicate with ports 26 thereby communicating the primary string inner bore with that portion of the well annulus between the permanent packer and the surface.

At this time, displacement fluid can be pumped down the conduit strings to displace the heavy fluids out into the annulus and up to the surface, or they may be reversed out by pumping displacement fluids down the f annulus and up the conduit strings. The secondary pumped down the secondary string to seat in sleeve 17. Application of pressure in the secondary string acts through ports 25 against shoulders 44- and 48 thereby driving the closing sleeve 47 downward thereby moving piston sleeve 27 back downward to cover ports 26 by straddling the ports with seals 38 and 39.

When the downward movement of sleeves 47 and 27 has continued long enough to align locking pins 61 with locking groove 33, the pins are urged inward into the groove thereby locking the valve in a permanently closed orientation. AT this time, if desirable, both strings may be pressurized sufficiently to shear the rings 18 and open the bore passages through the conduits by pumping ball and seat valves 17 and 21 down and out of the conduit.

Thus the advantages of this invention are clear; it allows the use of a circulating valve without having to manipulate the tubing to open and close the valve. This also allows the circulation of completion fluids without having to remove tubing seals from the permanent packer. These advantages save rig-time and reduce hazards and equipment damage while displacing fluids. This apparatus also allows pressure testing of the permanent packer before displacing and allows displacing of the long string without 'unsetting the permanent packer. Opening and closing of the circulating valve can be accomplished independently of the operation of the dual production packer and no wireline tools are needed in the operation.

Although a specific preferred embodiment of the present invention has been described in the detailed description above, the description is not intended to limit the invention to the particular forms or embodiments disclosed herein, since they are to be recognized as illustrative rather than restrictive and it will be obvious to those skilled in the art that the invention is not so limited. For example, whereas O-ring seals and shear rings are described in the apparatus it is obvious that other seal means and different shear means could be utilized. Furthermore, other types of pump down valves could be used in place of the ball and seat valves depicted. For instance, wireline retrievable plugs could be used in place of the ball valves. Furthermore, the dual string circulating valve disclosed herein is extremely advantageous for use between two dual packers in a "stacked dual installation where the upper packer is a primary-set dual packer. Since the circulating valve is normally opened by pressurizing the primary string, after this string is opened for circulating, the packer cannot be set.

By utilizing this apparatus between the two dual packers in the stacked installation and rotating the circulating tool 180, it can be converted to a secondary string actuated circulating assembly, thereby allowing later setting of the primary set packer after circulating between the dual packers.

Also, it is clear that while the ball and seat valves are illustrated and described as being located directly below the mandrels l1 and 12, it would be possible to utilize these mechanisms at any location in the tubing strings below the mandrels without greatly reducing the efficiency of the invention.

The invention is declared to cover all changes and modifications of the specific example of the invention herein disclosed for purposes of illustration, which do not constitute departures from the spirit and scope of the invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

l. A well valve assembly for use in dual production strings, said assembly comprising:

a tubular elongated primary mandrel having connection means at each end thereof for interconnection with other tubular sections;

a tubular elongated secondary mandrel in generally parallel orientation with said primary'mandrel;

mary mandrel port means to said first pressure responsive means, whereby said body member ports are placed in communication with said primary mandrel ports; and second pressure responsive means on said secondary mandrel in communication with said secondary mandrel ports and arranged to move said body member in response to fluid pressure applications to said secondary mandrel, whereby said body member is moved to block fluid communication from said primary mandrel port means to said body member port means. 2. The well valve assembly of claim 1 further comprising shear means between said body member and said primary mandrel, said shear means arranged to frangibly attach said body member to said primary mandrel to temporarily prevent slidable movement therebetween.

3. The well valve assembly of claim 1 further com.- prising selective locking means between said body member and said primary mandrel and arranged to abut said body member and said primary mandrel and prevent telescopic movement therebetween when said body member achieves a preselected position on said primary mandrel.

4. The well valve assembly of claim 3 wherein said selective locking means further comprises:

locking pin means slidably mounted in said body member;

resilient biasing means abutting said locking pin means and urging said locking pin means towards said primary mandrel;

retaining means in said body member for preventing said locking pin means from moving completely out of said body; and,

abutment channel means formed in said primary mandrel and adapted to fittingly receive said locking pin means.

5. The well valve assembly of claim 1 further comprising rigid attachment means fixedly connected to said primary mandrel and movably connected to said secondary mandrel, said attachment means arranged to allow limited axial movement of said secondary mandrel and unlimited rotational movement of said secondary mandrel.

6. The well valve assembly of claim wherein said attachment means comprises: 1

an attachment body having two bore passages therethrough containing said primary and secondary mandrels;

the first of said passages having connection means therein;

connection means on said primary mandrel adapted to be secured into said bore passage connection means;

abutment means in the second of said bore passages,

said abutment means abutting an inner shoulder formed in said second bore passage and projecting radially inward into said bore passage;

an elongated annular channel formed in said secondary mandrel, adapted to receive said abutment means, and substantially longer than said abutment means; and,

an abutment sleeve inserted concentrically in said second bore passage, fixedly attached therein, and abutting said abutment means in clamping arrangement with said inner shoulder. 7. The well valve assembly of claim 1 wherein said first pressure responsive means further comprises:

an external annular piston shoulder formed on said primary mandrel in close proximity to said primary mandrel port means;

an expansion chamber formed annularly in said body member adjacent said piston shoulder and arranged to receive said piston shoulder therein, said chamber arranged to communicate with said primary mandrel port means in a first position of said body member on said primary mandrel;

opposed pressure areas on said piston shoulder and in said chamber arranged to receive fluid pressure in said chamber and move in opposite directions; and,

seal means between said primary mandrel and said body member above and below said expansion chamber.

8. The well valve assembly of claim 1 wherein said second pressure responsive means comprises:

annular piston shoulder means formed on said secondary mandrel in close proximity to said secondary mandrel port means;

piston sleeve means slidably encircling said shoulder means and having an inwardly projecting annular shoulder slidably contacting said secondary mandrel;

an expansion chamber formed between said piston shoulder means and said inwardly projecting annular shoulder and concentrically between said secondary mandrel and said piston sleeve means, said chamber arranged to be placed in communication with said secondary mandrel port means;

opposed pressure responsive areas on said piston shoulder means and said inwardly projecting annular shoulder in said expansion chamber; and,

seal means between said piston sleeve means and said secondary mandrel above and below said expansion chamber.

9. The well valve assembly of claim 1 further comprising valve seat means frangibly attached to each of said mandrels; each said valve seat means adapted to receive a valve member in sealing relationship therein to close the inner bore of each said mandrel.

10. A dual circulating valve assembly for use in dual conduit production strings, comprising:

a generally circular body member'having two aligned cylindrical bore passages extending therethrough;

an elongated tubular primary mandrel extending telescopically through the first of said bore passages;

piston shoulder means on said primary mandrel and port means through the wall of said primary mandrel in close proximity to said shoulder means;

piston chamber means in said first bore passage arranged to receive said shoulder means;

an elongated tubular secondary mandrel extending through the second of said bore passages and slidably and rotatably held therein;

port means through the wall of said secondary mandrel;

seocnd piston means in said valve assembly arranged in conjunction with said secondary mandrel port.

means to receive fluidic pressure therethrough and further arranged to apply force to said body memher; and,

flow passage means from said primary mandrel through said body member, said flow passage meansarranged to be opened and closed by axial movement of said body member on said primary mandrel.

11. The circulating valve assembly of claim 10 wherein said primary and secondary mandrels and said body member are all cylindrical in configuration and are arranged so that their longitudinal axes are generally parallel.

12. The circulating valve assembly of claim 10 further comprising preselective resiliently biased locking means in said body member arranged to abut said primary mandrel and lock said mandrel to said body member when said body member is located on said mandrel such as to position said locking means over an abutment channel formed in said primary mandrel; said abutment channel adapted to receive said locking means.

13. The circulating valve of claim 12 further comprising frangible shear means initially securing said body member to said primary mandrel in a position blocking said primary mandrel-port means.

14. The circulating valve assembly of claim 13 wherein said second piston means comprises:

an annular piston shoulder formed externally on said secondary mandrel and arranged to communicate with said secondary mandrel port means;

a slidable external piston sleeve mounted slidably on said annular piston shoulder;

an inner annular sleeve shoulder internally formed in said sleeve and slidably contacting said secondary mandrel opposite said secondary port means from said annular piston shoulder;

first seal means between said annular piston shoulder and said piston sleeve; and,

second seal means between said sleeve shoulder and said secondary mandrel.

15. The circulating valve assembly of claim 14 wherein said piston sleeve is abuttingly arranged against said body member.

16. The circulating valve assembly of claim 15 further comprising a valve seat conduit attached to each of said mandrels, with each said conduit containing therein a valve seat sleeve frangibly attached to said conduit, said seat sleeve adapted to receive in sealing engagement a valve element and arranged to block passage through each said conduit upon seating of a valve element therein.

17. The circulating valve assembly of claim 16 further comprising abutment and assembly means fixedly attached to said primary mandrel and movably secured to said secondary mandrel and arranged to allow unlimited rotational movement and restricted axial movement of said secondary mandrel therein; said attachment and assembly means comprising:

an attachment body encircling both of said mandrels and arranged to limit downward movement of said body member by abutment therewith;

an annular abutment ring located concentrically within said attachment body and abutting an inner annular shoulder in said attachment body; and,

an assembly ring securedly attached to .said attachment body and abutting and clamping said abutment ring in said body;

said abutment ring projecting radially inwardly from said attachment body, and said secondary mandrel having an elongated peripheral abutment channel formed thereon substantially larger than said abutment ring and arranged to receive said abutment ring in slidable contact therein.

18. A dual string valve assembly for completion and production of multizone oil wells, said valve assembly comprising:

a generally cylindrical body having two cylindrical bore passages extending axially therethrough;

a primary mandrel slidably mounted in one of said bore passages, said mandrel having an open bore therethrough, primary port means through the wall thereof, and primary piston shoulder means lo cated externally thereon;

a tubular secondary mandrel slidably located in the second of said bore passages and having secondary port means through the wall thereof and secondary piston shoulder means thereon;

a piston chamber formed internally in the wall of said body in said first bore passage and adapted to receive said primary piston shoulder means slidably and sealingly therein, said chamber arranged to be placed in communication with said primary port means;

a secondary piston sleeve slidably mounted on said secondary piston shoulder and said secondary mandrel and having an enlarged inner bore section forming a secondary chamber in communication with said secondary port means;

frangible shear means attaching said body to said primary mandrel; and,

attachment means securedly attached to said primary mandrel in abutting relationship with said body, and movably attached to said secondary mandrel to allow unlimited rotational and restricted axial movement-of said secondary mandrel in said at tachment means.

19. The valve assembly of claim 18 further comprising:

a plurality of resiliently biased locking members slidably mounted in said body member and urged into abutment with said primary mandrel;

locking abutment channel means on said mandrel adapted to receive said locking members in abutting relationship therewith; and,

valve seating means attached to the lower end of each said mandrel, having a flow passage therethrough, and adapted to receive a valve member in seated relationship therein to block said flow passage.

20. The valve assembly of claim 19 wherein said valve seating means on said mandrels each comprises a tubular conduit containing a valve seating sleeve having a bevelled valve seat circumscribing a flow passage therethrough, each said seating sleeve being frangibly secured to said conduit; and,

said shear means in said body comprising a plurality of shearable screws secured in said body and projecting inwardly into said first bore passage, with said primary mandrel having a shear groove formed peripherally thereon and arranged to receive said shearable screws in abutment therein.

l l= l= l 

1. A well valve assembly for use in dual production strings, said assembly comprising: a tubular elongated primary mandrel having connection means at each end thereof for interconnection with other tubular sections; a tubular elongated secondary mandrel in generally parallel orientation with said primary mandrel; both of said mandrells having port means through the walls thereof; a body member encircling both said mandrels in relatively snug slidable relationship, said body member having port means through one side thereof; first pressure responsive means between said primary mandrel and said body member and communicating with said port means in said primary mandrel; said pressure responsive means arranged to move said body member axially on said primary mandrel upon application of fluid pressure through said primary mandrel port means to said first pressure responsive means, whereby said body member ports are placed in communication with said primary mandrel ports; and second pressure responsive means on said secondary mandrel in communication with said secondary mandrel ports and arranged to move said body member in response to fluid pressure applications to said secondary mandrel, whereby said body member is moved to block fluid communication from said primary mandrel port means to said body member port means.
 2. The well valve assembly of claim 1 further comprising shear means between said body member and said primary mandrel, said shear means arranged to frangibly attach said body member to said primary mandrel to temporarily prevent slidable movement therebetween.
 3. The well valve assembly of claim 1 further comprising selective locking means between said body member and said primary mandrel and arranged to abut said body member and said primary mandrel and prevent telescopic movement therebetween when said body member achieves a preselected position on said primary mandrel.
 4. The well valve assembly Of claim 3 wherein said selective locking means further comprises: locking pin means slidably mounted in said body member; resilient biasing means abutting said locking pin means and urging said locking pin means towards said primary mandrel; retaining means in said body member for preventing said locking pin means from moving completely out of said body; and, abutment channel means formed in said primary mandrel and adapted to fittingly receive said locking pin means.
 5. The well valve assembly of claim 1 further comprising rigid attachment means fixedly connected to said primary mandrel and movably connected to said secondary mandrel, said attachment means arranged to allow limited axial movement of said secondary mandrel and unlimited rotational movement of said secondary mandrel.
 6. The well valve assembly of claim 5 wherein said attachment means comprises: an attachment body having two bore passages therethrough containing said primary and secondary mandrels; the first of said passages having connection means therein; connection means on said primary mandrel adapted to be secured into said bore passage connection means; abutment means in the second of said bore passages, said abutment means abutting an inner shoulder formed in said second bore passage and projecting radially inward into said bore passage; an elongated annular channel formed in said secondary mandrel, adapted to receive said abutment means, and substantially longer than said abutment means; and, an abutment sleeve inserted concentrically in said second bore passage, fixedly attached therein, and abutting said abutment means in clamping arrangement with said inner shoulder.
 7. The well valve assembly of claim 1 wherein said first pressure responsive means further comprises: an external annular piston shoulder formed on said primary mandrel in close proximity to said primary mandrel port means; an expansion chamber formed annularly in said body member adjacent said piston shoulder and arranged to receive said piston shoulder therein, said chamber arranged to communicate with said primary mandrel port means in a first position of said body member on said primary mandrel; opposed pressure areas on said piston shoulder and in said chamber arranged to receive fluid pressure in said chamber and move in opposite directions; and, seal means between said primary mandrel and said body member above and below said expansion chamber.
 8. The well valve assembly of claim 1 wherein said second pressure responsive means comprises: annular piston shoulder means formed on said secondary mandrel in close proximity to said secondary mandrel port means; piston sleeve means slidably encircling said shoulder means and having an inwardly projecting annular shoulder slidably contacting said secondary mandrel; an expansion chamber formed between said piston shoulder means and said inwardly projecting annular shoulder and concentrically between said secondary mandrel and said piston sleeve means, said chamber arranged to be placed in communication with said secondary mandrel port means; opposed pressure responsive areas on said piston shoulder means and said inwardly projecting annular shoulder in said expansion chamber; and, seal means between said piston sleeve means and said secondary mandrel above and below said expansion chamber.
 9. The well valve assembly of claim 1 further comprising valve seat means frangibly attached to each of said mandrels; each said valve seat means adapted to receive a valve member in sealing relationship therein to close the inner bore of each said mandrel.
 10. A dual circulating valve assembly for use in dual conduit production strings, comprising: a generally circular body member having two aligned cylindrical bore passages extending therethrough; an elongated tubular primary mandrel extending telescopically through the first of said bore passages; piston shoulder means on said priMary mandrel and port means through the wall of said primary mandrel in close proximity to said shoulder means; piston chamber means in said first bore passage arranged to receive said shoulder means; an elongated tubular secondary mandrel extending through the second of said bore passages and slidably and rotatably held therein; port means through the wall of said secondary mandrel; seocnd piston means in said valve assembly arranged in conjunction with said secondary mandrel port means to receive fluidic pressure therethrough and further arranged to apply force to said body member; and, flow passage means from said primary mandrel through said body member, said flow passage means arranged to be opened and closed by axial movement of said body member on said primary mandrel.
 11. The circulating valve assembly of claim 10 wherein said primary and secondary mandrels and said body member are all cylindrical in configuration and are arranged so that their longitudinal axes are generally parallel.
 12. The circulating valve assembly of claim 10 further comprising preselective resiliently biased locking means in said body member arranged to abut said primary mandrel and lock said mandrel to said body member when said body member is located on said mandrel such as to position said locking means over an abutment channel formed in said primary mandrel; said abutment channel adapted to receive said locking means.
 13. The circulating valve of claim 12 further comprising frangible shear means initially securing said body member to said primary mandrel in a position blocking said primary mandrel port means.
 14. The circulating valve assembly of claim 13 wherein said second piston means comprises: an annular piston shoulder formed externally on said secondary mandrel and arranged to communicate with said secondary mandrel port means; a slidable external piston sleeve mounted slidably on said annular piston shoulder; an inner annular sleeve shoulder internally formed in said sleeve and slidably contacting said secondary mandrel opposite said secondary port means from said annular piston shoulder; first seal means between said annular piston shoulder and said piston sleeve; and, second seal means between said sleeve shoulder and said secondary mandrel.
 15. The circulating valve assembly of claim 14 wherein said piston sleeve is abuttingly arranged against said body member.
 16. The circulating valve assembly of claim 15 further comprising a valve seat conduit attached to each of said mandrels, with each said conduit containing therein a valve seat sleeve frangibly attached to said conduit, said seat sleeve adapted to receive in sealing engagement a valve element and arranged to block passage through each said conduit upon seating of a valve element therein.
 17. The circulating valve assembly of claim 16 further comprising abutment and assembly means fixedly attached to said primary mandrel and movably secured to said secondary mandrel and arranged to allow unlimited rotational movement and restricted axial movement of said secondary mandrel therein; said attachment and assembly means comprising: an attachment body encircling both of said mandrels and arranged to limit downward movement of said body member by abutment therewith; an annular abutment ring located concentrically within said attachment body and abutting an inner annular shoulder in said attachment body; and, an assembly ring securedly attached to said attachment body and abutting and clamping said abutment ring in said body; said abutment ring projecting radially inwardly from said attachment body, and said secondary mandrel having an elongated peripheral abutment channel formed thereon substantially larger than said abutment ring and arranged to receive said abutment ring in slidable contact therein.
 18. A dual string valve assembly for completion and production of multizone oil wells, said valve assembly comprising: a generally cyLindrical body having two cylindrical bore passages extending axially therethrough; a primary mandrel slidably mounted in one of said bore passages, said mandrel having an open bore therethrough, primary port means through the wall thereof, and primary piston shoulder means located externally thereon; a tubular secondary mandrel slidably located in the second of said bore passages and having secondary port means through the wall thereof and secondary piston shoulder means thereon; a piston chamber formed internally in the wall of said body in said first bore passage and adapted to receive said primary piston shoulder means slidably and sealingly therein, said chamber arranged to be placed in communication with said primary port means; a secondary piston sleeve slidably mounted on said secondary piston shoulder and said secondary mandrel and having an enlarged inner bore section forming a secondary chamber in communication with said secondary port means; frangible shear means attaching said body to said primary mandrel; and, attachment means securedly attached to said primary mandrel in abutting relationship with said body, and movably attached to said secondary mandrel to allow unlimited rotational and restricted axial movement of said secondary mandrel in said attachment means.
 19. The valve assembly of claim 18 further comprising: a plurality of resiliently biased locking members slidably mounted in said body member and urged into abutment with said primary mandrel; locking abutment channel means on said mandrel adapted to receive said locking members in abutting relationship therewith; and, valve seating means attached to the lower end of each said mandrel, having a flow passage therethrough, and adapted to receive a valve member in seated relationship therein to block said flow passage.
 20. The valve assembly of claim 19 wherein said valve seating means on said mandrels each comprises a tubular conduit containing a valve seating sleeve having a bevelled valve seat circumscribing a flow passage therethrough, each said seating sleeve being frangibly secured to said conduit; and, said shear means in said body comprising a plurality of shearable screws secured in said body and projecting inwardly into said first bore passage, with said primary mandrel having a shear groove formed peripherally thereon and arranged to receive said shearable screws in abutment therein. 